2) Edit bios to make mem clocks in 2d mode to match mem clocks in 3d mode, it’s a bit dangerous and not recomended info about it can be found here Insanelymac thread

3) This way is only for 4850 atm. OSX drivers get information about clock speed from ATY,bin_image variable from ioregistry, normaly it has bios dump natit got from your card, but, we can replace this content with anything we want, so I put modified 4850 bios into natit and no shakes, i think powerplay is working for downscaling core clocks. You can get it here – Natit with 4850 bios inside , install it after installing driver pkg from irc. it’s like second case without actual flashing 🙂
The bios I used for it –4850 bios no shakes